1. Field of the Invention
This invention relates to a sensor system which allows a trailing end of a hood of a vehicle to be lifted up a given height or a hood air bag, mounted in the vicinity of the hood, to be deployed, for absorbing an impact or shock from a secondary collision of an object on the hood during a frontal collision of the vehicle with the object.
2. Description of the Related Art
It has heretofore been proposed to provide a hood air bag sensor system for alleviating an impact shock to be applied to an object when a vehicle collides with the object and the object is jumped over a hood of the vehicle to encounter a secondary collision, as disclosed in, for example, a Japanese Patent Kokai (Laid-open) Publication NO. HEI-8-216826.
With such a sensor system, an impact load, which undergoes in a horizontal and frontal direction the collision of the vehicle against the object, is detected by a single bumper sensor which is mounted to a substantially central area of a front bumper in a widthwise direction of the vehicle. Upon receipt of output signals produced by the hood air bag sensor system involving such a bumper sensor, a control device functions to actuate a hood air bag.
However, the aforementioned hood air bag system encounters difficulty in accurately detecting the impact load to be applied to the object especially when the object collides with the front bumper a position displaced from the bumper sensor. In order to address this issue, for example, if a large number of load sensors or displacement sensors are mounted to the front bumpers, even though the load or displacement values are enabled to be accurately detected, other problems are encountered such as an increase in production cost or a decrease in productivity.
It is therefore an object of the present invention to provide a vehicular sensor system which can discriminate an object with increased accuracy with a reduced number of sensors.
According to an aspect of the present invention, there is provided a vehicular sensor system which is responsive to a collision of an object against a front bumper of a vehicle to allow either one of a lift-up operation of a rear trailing end of a hood of the vehicle and a deployment operation of a hood air bag, which is mounted in the vicinity of the hood, to be initiated, which comprises a plurality of bumper sensors mounted to the front bumper at positions spaced from one another in a widthwise direction of the vehicle, and a controller which converts signals, detected by the respective bumper sensors, into deformation speeds, with the deformation speeds, associated with the bumper sensors which are adjacent to one another, being added for controlling the either one of the lift-up operation of the trailing end of the hood and the deployment operation of the hood air bag to be initiated when the added result exceeds a predetermined threshold level.
With this arrangement, even when the object encounters the collision between the adjacent bumper sensors, addition of two deformation speeds is reflected with an increased deformation speed result to obtain the increased deformation speed even when the impact position of the object is displaced from the respective bumper sensors, thereby preventing an impact discriminating performance for the object from being deteriorated.
It is desirable that the controller includes a first deformation speed detector for converting a signal, which is detected by a first bumper sensor mounted at one side of the front bumper in the widthwise direction, into a first deformation speed, a second deformation speed detector for converting a signal, which is detected by a second bumper sensor mounted at a substantially central area of said front bumper, into a second deformation speed signal, a third deformation speed detector for converting the signal, which is detected by a third bumper sensor mounted at the other side of said front bumper in the widthwise direction, into a third deformation speed, a first adder for adding the first and second deformation speeds detected by the first and second deformation speed detectors, respectively, a second adder for adding the second and third deformation speeds detected by the second and third deformation speed detectors, respectively, a first comparator for comparing the first added deformation speed, which is added by the first adder, with a predetermined threshold level, a second comparator for comparing a second added deformation speed, which is added by the second adder, with the predetermined threshold level, and an actuation discriminator for initiating the either one of the lift-up operation of the trailing end of the hood and the deployment operation of the hood air bag when either one of the added deformation speeds compared with the first and second comparators exceeds the predetermined threshold level.
In this arrangement, since the detected deformation speeds are added by the first and second adders and the respective deformation speeds are compared with the first and second comparators, respectively, with the actuation discriminator serving to discriminate on the basis of the compared deformation speeds, for example, even when the object encounters the collision between the first and second bumper sensors, the impact of the object is enabled to be accurately discriminated, enabling the improvement over the discriminating accuracy for the impact of the object even with fewer bumper sensors.
Preferably, the controller controls to initiate the either one of the lift-up operation of the trailing end of the hood and the deployment operation of the hood air bag when the signals, which are detected while the respective bumper sensors, are converted into the deformation speeds with the deformation speeds, associated with the bumper sensors which are adjacent to one another, being added and the added result exceeds the first predetermined threshold level, and when the respective deformation speeds are converted into respective deformation quantities while the two deformation quantities are added and the added result exceeds the second predetermined threshold level.
In a preferred form, the controller further includes a first deformation speed detector for converting the signal, which is detected by a first bumper sensor mounted at one side of the front bumper in the widthwise direction, into a first deformation speed, a second deformation speed detector for converting the signal, which is detected by a second bumper sensor mounted at the other side of the front bumper, into a second deformation speed signal, a first adder for adding the first and second deformation speeds detected by the first and second deformation speed detectors, respectively, a first comparator for comparing first added deformation speed, which is added by the first adder, with a first predetermined threshold level, a first deformation quantity detector for converting a first deformation speed, which is converted by the first deformation speed detector, into a first deformation quantity, a second deformation quantity detector for converting a second deformation speed, which is converted by the second deformation speed detector, into a second deformation quantity, a second adder for adding the first and second deformation quantities converted by the first and second deformation quantity detectors, respectively, second comparator for comparing an added deformation quantity, which is added by the second adder, with a second predetermined threshold level, and an actuation discriminator for initiating either one of the lift-up operation of the trailing end of the hood and the deployment operation of the hood air bag when the added deformation speed, which is compared with the first comparator, exceeds the first threshold level and when the added deformation quantity, which is compared with the second comparator, exceeds the second threshold level.
In this arrangement, when the object encounters the collision between the first and second bumper sensors, the actuation discriminator executes required discrimination on the basis of the deformation speed compared by the first comparator and the deformation quantity compared by the second comparator. As a result, it becomes possible to accurately discriminate an object collision with a reduced number of sensors.